5-Azacytidine for the treatment of myelodysplastic syndromes

Emerging applications of hypomethylating agents in the treatment of glioblastoma (Review)

DNA hypomethylating agents (HMAs) such as decitabine and 5-azacytidine have established roles in the treatment paradigms for myelodysplastic syndrome and acute myelogenous leukemia, where they are considered to exert their anticancer effects by restoring the expression of tumor suppressor genes. Due to their relatively favorable adverse effect profile and known ability to pass through the blood-brain barrier, applications in the treatment of glioblastoma (GBM) and other central nervous system malignancies are under active investigation. The present review examines the types of HMAs currently available, their known and less-understood antineoplastic mechanisms, and the evidence to date of their preclinical and clinical efficacy in glioblastoma and other solid malignancies. The present review discusses the potential synergies HMAs may have with established and emerging GBM treatments, including temozolomide, immune checkpoint inhibitors and cancer vaccines. Recent successes and setbacks in clinical trials for newly diagnosed and recurrent GBM are summarized in order to highlight opportunities for HMAs to improve therapeutic responses. Challenges for future clinical trials are also assessed.

Critical appraisal of epigenetic regulation of galectins in cancer

Galectins are defined as the glycan-binding protein containing either one or two carbohydrate-binding domains and participate in various biological functions such as developmental processes, vascularisation programs, cell migration, and immune-regulation and apoptosis. Galectins are also linked to many diseases, including cancer. They are widely spread in extracellular and intracellular spaces, and their altered expression in cancer leads to tumor progression, metastasis, angiogenesis and stemness through different signalling pathways. Promoter methylation, microRNA, and histone modification constitute the epigenetic changes that regulate galectin activity in cancer. Our review discusses the concept of epigenetics in cancer and how the aforementioned factors i.e., promoter methylation, histone modification, change in miRNAs expression affect the glycomic changes in malignancies.

Interactivity of biochemical and physical stimuli during epigenetic conditioning and cardiomyocytic differentiation of stem and progenitor cells derived from adult hearts

Mixed populations of cardiosphere-derived stem and progenitor cells containing proliferative and cardiomyogenically committed cells were obtained from adult rat hearts. The cells were cultured in either static 2D monolayers or dynamic 3D scaffold systems with fluid flow. Cardiomyocyte lineage commitment in terms of GATA4 and Nkx2.5 expression was significantly enhanced in the dynamic 3D cultures compared with static 2D conditions. Treatment of the cells with 5-azacytidine (5-aza) produced different responses in the two culture systems, as activity of this chemical epigenetic conditioning agent depended on the cell attachment and hydrodynamic conditions provided during culture. Cell growth was unaffected by 5-aza in the static 2D cultures but was significantly reduced under dynamic 3D conditions relative to untreated controls. Myogenic differentiation measured as Mef2c expression was markedly upregulated by 5-aza in the dynamic 3D cultures but downregulated in the static 2D cultures. The ability of the physical environment to modulate the cellular cardiomyogenic response to 5-aza underscores the interactivity of biochemical and physical stimuli applied for cell differentiation. Accordingly, observations about the efficacy of 5-aza as a cardiomyocyte induction agent may not be applicable across different culture systems. Overall, use of dynamic 3D rather than static 2D culture was more beneficial for cardio-specific myogenesis than 5-aza treatment, which generated a more ambiguous differentiation response.

Immunemodulatory Effects of 5-Azacitidin Through Expansion of Functional Regulatory T Cells on Paraneoplastic Inflammation Associated With Myelodysplastic Syndromes: A Case Report

Myelodysplastic syndrome (MDS) is a heterogeneous group of clonal disorders of hematopoietic stem cells, characterized by dysplastic hematopoiesis and dysregulated immune system resulting in various clinical conditions. Paraneoplastic inflammatory syndromes, which are well known to be associated with MDS, show response to immune-modulated therapy and often disappear during the course of hematologic management. Azacitidine (5-Aza) was shown to prolong survival of high-risk MDS patients, however, the effects of 5-Aza on paraneoplastic inflammation in MDS have yet to be elucidated. 5-Aza was administered to a 60-year-old man with MDS accompanying Sweet’s syndrome at a dose of 75 mg/m²/daily subcutaneously for 7 days every 28 days. 5-Aza was not only effective in controlling systemic symptoms caused by paraneoplastic inflammation, but hematologic improvements were also observed after four cycles of the 5-Aza treatment. Immune profiling in peripheral blood before and after 5-Aza treatment revealed that the effector and naive regulatory T cells in lymphocytes drastically increased after the 5-Aza treatment, i.e., 5-Aza might induce a shift in lymphocytic populations toward immunosuppression in this patient. Our results raised the immune-mediated effect of 5-Aza on both dysplastic hematopoiesis and paraneoplastic inflammation in myelodyplastic syndromes.

Altered expression of miRNAs and methylation of their promoters are correlated in neuroblastoma

Neuroblastoma is the most common human extracranial solid tumor during infancy. Involvement of several miRNAs in its pathogenesis has been ascertained. Interestingly, most of their encoding genes reside in hypermethylated genomic regions: thus, their tumor suppressor function is normally disallowed in these tumors. To date, the therapeutic role of the demethylating agent 5′-Aza-2 deoxycytidine (5'-AZA) and its effects on miRNAome modulation in neuroblastoma have not been satisfactorily explored. Starting from a high-throughput expression profiling of 754 miRNAs and based on a proper selection, we focused on miR-29a-3p, miR-34b-3p, miR-181c-5p and miR-517a-3p as candidate miRNAs for our analysis. They resulted downregulated in four neuroblastoma cell lines with respect to normal adrenal gland. MiRNAs 29a-3p and 34b-3p also resulted downregulated in vivo in a murine neuroblastoma progression model. Unlike the amount of methylation of their encoding gene promoters, all these miRNAs were significantly overexpressed following treatment with 5′-AZA. Transfection with candidate miRNAs mimics significantly decreased neuroblastoma cells proliferation rate. A lower expression of miR-181c was significantly associated to a worse overall survival in a public dataset of 498 neuroblastoma samples (http://r2.amc.nl). Our data strongly suggest that CDK6, DNMT3A, DNMT3B are targets of miR-29a-3p, while CCNE2 and E2F3 are targets of miR-34b-3p. Based on all these data, we propose that miR-29a-3p, miR-34b-3p, miR-181c-5p and miR-517a-3p are disallowed tumor suppressor genes in neuroblastoma and suggest them as new therapeutic targets in neuroblastoma.

Epigenetic regulation of hepatitis B virus covalently closed circular DNA: Implications for epigenetic therapy against chronic hepatitis B

Hepatitis B virus (HBV) infection represents a significant public health burden worldwide. Although current therapeutics manage to control the disease progression, lifelong treatment and surveillance are required because drug resistance develops during treatment and reactivations frequently occur following medication cessation. Thus, the occurrence of hepatocellular carcinoma is decreased, but not eliminated. One major reason for failure of HBV treatment is the inability to eradicate or inactivate the viral covalently closed circular DNA (cccDNA), which is a stable episomal form of the viral genome decorated with host histones and nonhistone proteins. Accumulating evidence suggests that epigenetic modifications of cccDNA contribute to viral replication and the outcome of chronic HBV infection. Here, we summarize current progress on HBV epigenetics research and the therapeutic implications for chronic HBV infection by learning from the epigenetic therapies for cancer and other viral diseases, which may open a new venue to cure chronic hepatitis B. (Hepatology 2017;66:2066-2077).

Autophagy in acute leukemias: a double-edged sword with important therapeutic implications

Macroautophagy, usually referred to as autophagy, is a degradative pathway wherein cytoplasmatic components such as aggregated/misfolded proteins and organelles are engulfed within double-membrane vesicles (autophagosomes) and then delivered to lysosomes for degradation. Autophagy plays an important role in the regulation of numerous physiological functions, including hematopoiesis, through elimination of aggregated/misfolded proteins, and damaged/superfluous organelles. The catabolic products of autophagy (amino acids, fatty acids, nucleotides) are released into the cytosol from autophagolysosomes and recycled into bio-energetic pathways. Therefore, autophagy allows cells to survive starvation and other unfavorable conditions, including hypoxia, heat shock, and microbial pathogens. Nevertheless, depending upon the cell context and functional status, autophagy can also serve as a death mechanism. The cohort of proteins that constitute the autophagy machinery function in a complex, multistep biochemical pathway which has been partially identified over the past decade. Dysregulation of autophagy may contribute to the development of several disorders, including acute leukemias. In this kind of hematologic malignancies, autophagy can either act as a chemo-resistance mechanism or have tumor suppressive functions, depending on the context. Therefore, strategies exploiting autophagy, either for activating or inhibiting it, could find a broad application for innovative treatment of acute leukemias and could significantly contribute to improved clinical outcomes. These aspects are discussed here after a brief introduction to the autophagic molecular machinery and its roles in hematopoiesis.

5-azacytidine promotes the transdifferentiation of cardiac cells to skeletal myocytes

The DNA methylation inhibitor 5-azacytidine is widely used to stimulate the cardiac differentiation of stem cells. However, 5-azacytidine has long been employed as a tool for stimulating skeletal myogenesis. Yet, it is unclear whether the ability of 5-azacytidine to promote both cardiac and skeletal myogenesis is dependent strictly on the native potential of the starting cell population or if this drug is a transdifferentiation agent. To address this issue, we examined the effect of 5-azacytidine on cultures of adult mouse atrial tissue, which contains cardiac but not skeletal muscle progenitors. Exposure to 5-azacytidine caused atrial cells to elongate and increased the presence of fat globules within the cultures. 5-Azacytidine also induced expression of the skeletal myogenic transcription factors MyoD and myogenin. 5-Azacytidine pretreatments allowed atrial cells to undergo adipogenesis or skeletal myogenesis when subsequently cultured with either insulin and dexamethasone or low-serum media, respectively. The presence of skeletal myocytes in atrial cultures was indicated by dual staining for myogenin and sarcomeric α-actin. These data demonstrate that 5-azacytidine converts cardiac cells to noncardiac cell types and suggests that this drug has a compromised efficacy as a cardiac differentiation factor.

Possible involvement of locus-specific methylation on expression regulation of leafy homologous gene (CiLFY) during precocious trifoliate orange phase change process

DNA methylation plays an essential role in regulating plant development. Here, we described an early flowering trifoliate orange (precocious trifoliate orange, Poncirus trifoliata L. Raf) was treated with 5-azacytidine and displayed a number of phenotypic and developmental abnormalities. These observations suggested that DNA methylation might play an important role in regulating many developmental pathways including early flowering trait, and then the expression level of five key or integrated citrus flowering genes were analyzed. Our results showed that FLOWERING LOCUS T (CiFT) relative expression level was increased with the increasing concentrations of 5-AzaC. However, LEAFY (CiLFY), APETELA1 (CiAP1), TERMINAL FLOWER1 (CiTFL1), and FLOWERING LOCUS C (CiFLC) showed highest relative expression levels at 250 µΜ treatment, while decreased sharply at higher concentrations. In order to further confirm DNA methylation affects the expression of these genes, their full-length sequences were isolated by genome-walker method, and then was analyzed by using bioinformatics tools. However, only one locus-specific methylation site was observed in CiLFY sequence. Therefore, DNA methylation level of the CiLFY was investigated both at juvenile and adult stages of precocious trifoliate orange by bisulfate sequencing PCR; it has been shown that the level of DNA methylation was altered during phase change. In addition, spatial and temporal expression patterns of CiLFY promoter and a series of 5′ deletions were investigated by driving the expression of a β-glucuronidase reporter gene in Arabidopsis. Exogenous GA₃ treatment on transgenic Arabidopsis revealed that GA₃ might be involved in the developmental regulation of CiLFY during flowering process of precocious trifoliate orange. These results provided insights into the molecular regulation of CiLFY gene expression, which would be helpful for studying citrus flowering.